In substrate processing, such processes as thin film formation, surface modification, and dry etching are performed on a substrate in a vacuum. Such substrate processing is often performed with the substrate placed on a tray. For instance, in the processing disclosed in Patent Document 1, a substrate is dropped into the recess of a bottomed tray, and a ring chuck is further placed thereon. In this state, the substrate along with the tray is electrostatically adsorbed onto an electrostatic chuck and processed.